A number of studies have been made on a network device. The most widespread network device uses an IP (Internet protocol) network. An MPLS (multiprotocol labeled switching) is a network device having a mechanism of automatically generating a route. In addition, there are an AODV (Ad-hoc on-demand vector) and an OLSR (optimized link state routing).
In the IP network device, a route is determined according to an IP address. Since an IP address has a tree structure, a frame can be transmitted to a final target terminal by transmitting an upper part of IP address to a network device managing a matching IP network. A route is determined by an IP address system. Which network device manages which IP network is regulated by a routing table. The routing table is mainly set manually, but can also be automatically updated by a RIP (routing information protocol). An RIP is a system for broadcasting an IP network managed by a network device to the surroundings, and confirming the IP network managed by each network device.
In the MPLS, networks are separated into network devices called LSRs (label switch routers) and external networks. A frame from an external network is taken into an internal network by a network device spanning an external network called an edge node and an internal network. In this case, a label is inserted into the head of the external frame. Each LSR has a label transfer table. The label transfer table holds a label of an input frame, a label of an output frame, and a destination. The LSR retrieves a label of an input frame, finds a corresponding label from the label transfer table, rewrites the label into the label of the output frame, and transmits it to a corresponding destination. It is performed by the LDP (label distribution protocol) of the label transfer table. The LDP first generates a routing table by the RIP etc., adds a label to the table, and transmits a notification between the adjacent nodes.
The AODV is a method of finding a route to a target node device after another node communication node device repeats a broadcast using the broadcast in searching for a route. The communication node device transmits a frame called a “route request (RREQ)” to the surroundings to find a target route. The frame describes a target communication node ID to be retrieved. When a surrounding communication node device is not retrieved by itself, it newly generates a RREQ frame, and repeatedly performs a broadcast to the surroundings. In this case, each communication node device records from which adjacent communication node device the received message is transmitted. When the RREQ frame reaches a target communication node device, the target communication node device generates a “route reply (RREP)” frame, and transmits the RREP frame to a source node so that the route of the transmitted RREQ frame can be traced. Thus, a bidirectional communication route is generated.
In the OLSR (optimized link state routing), the entire network is grasped by periodically exchanging a frame among the communication node devices and detecting a route to a target communication node. A communication node device periodically transmits a hello frame to notify each other of the existence. When the existence of a communication node device as a communication partner is known, a route for flooding in efficiently distributing a frame to the entire network is generated next. It is called “MPR (multipoint relay)”. By the MPR, a frame can be efficiently broadcast from each communication node device to the entire network. Next, using the MPR, all node devices can be informed of the network topology by mutually distributing a TC (topology control) frame as a route generating message to one another. When a frame is to be transmitted to a target communication node device, a network topology known to the source communication node device is referred to, and the frame is committed to an adjacent destination communication node device. The adjacent node device performs a similar process, and finally transmits the frame to the target node device.
In an Ad-hoc wireless communication network, as a well-known technique, each node broadcasts the information as a hello message including the information about the existence of the local node and the route metric to the local node. Another node which receives the hello message adds to the received route metric the route metric for the route between the node which has broadcast the hello message and the local node. The resultant route metric is used in the technique (for example, the patent document 1). The route metric in this case can be a value indicating the costs at the source and the destination calculated by a factor such as a hop count, link quality, etc.    Patent Document 1: National Publication of International Patent Application No. 2006-526937